The long-term objective of this proposal is to develop new approaches to the treatment of cardiomyopathy. In particular, this project will evaluate the feasibility of using vectors based on the non-pathogenic parvo virus, adeno-associated virus (aav), as vehicles for cardiac gene therapy. For this purpose the inherited hypertrophic cardiomyopathy, infantile Pompe's disease, will be used as a model system. Pompe's disease results from a deficiency of acid a-glucosidase (gaa), the lysosomal hydrolase that degrades glycogen. In this lysosomal storage disorder, glycogen accumulates in the heart and striated muscle, leading to massive cardiac hypertrophy, weakened muscle contraction and reduced conduction. This proposal will assess the ability of this promising vector, aav, to provide long term, high-level delivery of gaa to cardiac and skeletal muscle. The first major goal is to examine the effects of aav-mediated gene transfer in several in vitro models, particularly in fibroblasts from patients with infantile Pompe's disease and in skeletal muscle cultures prepared from japanese quail with abnormally low levels of gaa. The impact of this gene transfer will be evaluated in the model systems by biochemical, immunological, and morphological methods. The second major goal of the proposal is to evaluate the ability of the aav vectors to deliver gaa in vivo to cardiac and skeletal muscle in mice. Two delivery strategies will be used: in vivo transduction of skeletal muscle with gaa-encoding aav vectors to provide a platform for local synthesis and secretion of the enzyme; and direct cardiac transduction with the aav vectors. Finally, one or both strategies will be adopted to reconstitute gaa activity in deficient quail embryos.